LED manufacturing frame and method of using the same for manufacturing LEDs

ABSTRACT

An LED manufacturing frame comprises a first tie bar extending longitudinally of the frame, a second tie bar also extending longitudinally of the frame substantially in parallel to the first tie bar, and plural groups of first to fourth consecutive leads connecting between the first and second tie bars. The first and third leads have respective extensions extending transversely beyond the first tie bar to provide first side pairs of chip bonding and wire bonding ends. Similarly, the second and fourth leads have respective extensions extending transversely beyond the second tie bar to provide second side pairs of chip bonding and wire bonding ends.

BACKGROUND OF THE INVENTION

1. Field of the Invention:

This invention relates to a frame which is used for manufacturing lightemitting diodes (commonly abbreviated as "LED"). The present inventionalso relates to a method of using such a frame for efficientlymanufacturing LEDs.

2. Description of the Prior Art:

Like other electronic components, LEDs are manufactured by using such aframe as shown in FIG. 7 of the accompanying drawings. Usually, theframe has a strip form with a limited length and is known as"leadframe".

As shown in FIG. 7, the frame or leadframe, generally designated byreference numeral 1, is prepared by punching a metal sheet to have abase bar 3 extending longitudinally of the frame and a tie bar 4 alsoextending longitudinally of the frame in parallel to the base bar 3. Thebase bar 3 is formed with a plurality of indexing holes 2 which are usedfor longitudinally transferring the frame 1.

Between the base bar 3 and the tie bar 4, there are multiple pairs ofleads 5, 6 arranged at a constant pitch longitudinally of the frame 1.The respective pairs of leads 5, 6 extend beyond the tie bar 4 toprovide corresponding pairs of chip bonding cup end 7 and wire bondingend 8. Near the pairs of cup end 7 and wire bonding end 8, therespective leads 5, 6 are connected together by a reinforcing bar 4aextending longitudinally of the frame 1 laterally outwardly of the tiebar 4, thereby increasing the supporting rigidity or stability for therespective pairs of cup end 5 and wire bonding end 6.

For manufacturing LEDs, the frame 1 is first introduced into a bondingunit (not shown) in which an LED chip 9 is bonded to each chip bondingcup end 7, as shown in FIG. 8. In the bonding unit, further, a metalwire 10 is bonded to the LED chip 9 and to a corresponding wire bondingend 8. Such a bonding operation is performed individually for therespective pairs of cup end 7 and wire bonding end 8 as the frame 1 istransferred stepwise by utilizing the indexing holes 2.

Then, the frame 1 is introduced into a molding unit (not shown) whereina resin package (not shown) is formed to enclose each pair of cup end 7and wire bonding end 8. The resin package may be made of a transparentresin material such as epoxy to have a general shape of a bullet.

Finally, the respective packaged LED devices are separated from theframe 1 by cutting the leads 5, 6 near the base bar 3 and by cutting thetie bar 4 and the reinforcing bar 4a near the respective leads 5, 6.Thus, product LED devices are obtained each of which has a pair of leads5, 6 extending from the unillustrated resin package.

The prior art described above is disadvantageous at least in thefollowing points.

First, the pairs of cup end 7 and wire bonding end 8 are provided onlyon one side of the frame 1. Since the spacing or pitch between therespective pairs of cup end 7 and wire bonding end 8 must be renderedsufficiently large to enable formation of the relatively bulky resinpackages, there is a limitation in increasing the number of obtainableLEDs per unit length of the frame. As a result, the productionefficiency lowers, and much portion of a metal sheet is wasted at thetime of punching it into the frame, thereby increasing the productioncost per LED.

Secondly, since the frame 1 has a strip-form with a limited length,plurality of such frames need be successively transferred and handled inactual manufacture of LEDs. Specifically, at the entrance and exit ofeach of the different process units (e.g. a bonding unit, a moldingunit, and etc.), the frames need be stacked in a frame magazine. Thus,it is necessary to provide some mechanism which individually picks upfrom or discharge into the frame magazine. It is further necessary toprovide some mechanism for transferring the frame magazine between thedifferent process units. As a result, the cost of the manufacturingapparatus is relatively high, but yet the production efficiency isrelatively low due to the need for individually handling the strip-likeframes.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide an LEDmanufacturing frame which provides a greatly increased number ofobtainable LEDs per unit length of the frame.

Another object of the invention is to provide a method of efficientlymanufacturing LEDs at a reduced cost from a continuous frame.

According to one aspect of the present invention, there is provided anLED manufacturing frame comprising: a first tie bar extendinglongitudinally of the frame; a second tie bar also extendinglongitudinally of the frame substantially in parallel to the first tiebar; first side pairs of chip bonding and wire bonding lead endsarranged transversely outwardly of the first tie bar substantially at aconstant pitch; and second side pairs of chip bonding and wire bondinglead ends arranged transversely outwardly of the second tie barsubstantially at the same pitch as the first side pairs of chip bondingand wire bonding lead ends.

In a preferred embodiment of the present invention, the first and secondtie bars are connected together by plural groups of first to fourthconsecutive leads. The first side pairs of chip bonding and wire bondinglead ends are provided by respective extensions of the first and thirdleads, whereas the second side pairs of chip bonding and wire bondinglead ends are provided by respective extensions of the second and fourthleads.

According to another aspect of the present invention, there is provideda method of manufacturing LEDs from a continuous frame which comprises:a first tie bar extending longitudinally of the frame; a second tie baralso extending longitudinally of the frame substantially in parallel tothe first tie bar; first side pairs of chip bonding and wire bondinglead ends arranged transversely outwardly of the first tie barsubstantially at a constant pitch; and second side pairs of chip bondingand wire bonding lead ends arranged transversely outwardly of the secondtie bar substantially at the same pitch as the first side pairs of chipbonding and wire bonding lead ends; the method comprising performing thefollowing process steps while transferring the continuous framelongitudinally thereof:

(a) bonding an LED chip to each of the chip bonding lead ends, andthereafter bonding a metal wire to the LED chip and to a correspondingwire bonding lead end;

(b) forming a resin package to enclose each pair of chip bonding andwire bonding lead ends together with the LED chip and the wire;

(c) longitudinally separating the frame into a first frame portion whichcontains the first tie bar together with the first side pairs of chipbonding and wire bonding lead ends, and a second frame portion whichcontains the second tie bar together with the second side pairs of chipbonding and wire bonding lead ends, the first and second frame portionsbeing used for subsequent transfer; and

(d) separating said each pair of chip bonding and wire bonding leadends, which has been enclosed in the resin package, from a correspondingone of the first and second frame portions to provide a product.

Preferably, the bonding step (a) is performed separately in twodifferent bonding units with respect to the first side pairs of chipbonding and wire bonding lead ends and the second side pairs of chipbonding and wire bonding lead ends, and the continuous frame is twistedby 180° between the respective bonding units. Similarly, it is alsoadvantageous that the molding step (b) is performed separately in twodifferent bonding units with respect to the first side pairs of chipbonding and wire bonding lead ends and the second side pairs of chipbonding and wire bonding lead ends, and the continuous frame is twistedby 180° between the respective molding units.

Other objects, features and advantages of the present invention willbecome apparent from the following detailed description of the preferredembodiments given with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a plan view showing a portion of an LED manufacturing frameaccording to the present invention;

FIG. 2 is a schematic view showing a method of manufacturing LEDs withthe use of the frame shown in FIG. 1;

FIG. 3 is a fragmentary plan view showing a bonding step of the LEDmanufacturing method;

FIG. 4 is also a fragmentary plan view, partially in section, showing amolding step of the LED manufacturing method;

FIG. 5 is a schematic plan view showing a cutting step of the LEDmanufacturing method;

FIG. 6 is a view showing a product separation step of the LEDmanufacturing method;

FIG. 7 is a plan view showing a prior art LED manufacturing frame; and

FIG. 8 is an enlarged fragmentary plan view showing a principal portionof the prior art frame.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIG. 1 of the accompanying drawings, there is shownan LED manufacturing frame according to the present invention. Theframe, which is generally designated by reference numeral 21, isprepared by punching a metal sheet. The frame 21 is substantiallycontinuous, and only a portion of it is shown in FIG. 1.

The frame 21 comprises a first tie bar 22a extending longitudinally ofthe frame along one side thereof, and a second tie bar 22b alsoextending longitudinally of the frame along the other side thereof inparallel to the first tie bar 22a. Between the first and second tie bars22a, 22b, there are multiple groups of first to fourth consecutive leads23a-23d arranged at a constant pitch longitudinally of the frame 21.

In each group of first to fourth leads, the first and third leads 23a,23c have paired extensions 23a', 23c' extending beyond the first tie bar22a widthwise (transversely) of the frame 21. The extension 23a' of thefirst lead 23a has a chip bonding cup end 24, whereas the extension 23c'of the third lead 23c has a wire bonding end 25. The respectiveextensions 23a', 23c' of the first and third leads 23a, 23c areconnected together by a first reinforcing bar 26a extendinglongitudinally of the frame 21 laterally outwardly of the first tie bar22a, thereby increasing the supporting rigidity or stability for the cupend 24 and the wire bonding end 25.

Similarly, the second and fourth leads 23b, 23d in each lead group havepaired extensions 23b', 23d' extending beyond the second tie bar 22bwidthwise (transversely) of the frame 21. The extension 23b' of thesecond lead 23b has a chip bonding cup end 24, whereas the extension23d' of the fourth lead 23d has a wire bonding end 25. The respectiveextensions 23b', 23d' of the second and fourth leads 23b, 23d areconnected together by a second reinforcing bar 26b extendinglongitudinally of the frame 21 laterally outwardly of the second tie bar22b, thereby increasing the supporting rigidity or stability.

FIG. 2 schematically illustrates a method and apparatus formanufacturing LEDs from the continuous LED manufacturing frame 21described above. In manufacture, the LED manufacturing frame 21 iscaused to longitudinally pass through the LED manufacturing apparatus27. This apparatus 27 mainly includes a first bonding unit 28a, a secondbonding unit 28b, a first molding unit 31a, a second molding unit 31b,and a frame cutting unit 34, all of which are arranged in succession inthe mentioned order.

In the first bonding unit 28a, an LED chip 29 is bonded to each cup end24 located closer to the first tie bar 22a, and a wire 30 of gold forexample is bonded to the thus mounted chip 29 and its counterpart wirebonding end 25, as shown in FIG. 3. A similar bonding operation is alsoperformed in the second bonding unit 28b with respect to each pair ofcup end 24 and wire bonding end 25 located closer to the second tie bar22b.

According to the illustrated embodiment, the frame 21 is twisted by 180°between the first and second bonding units 28a, 28b, as shown in FIG. 2.Thus, the respective bonding units 28a, 28b can be made to perform thebonding operation from the same side of the frame transfer path. As aresult, the respective bonding units 28a, 28b may have an identicalstructure, thereby contributing to a cost reduction.

In the first molding unit 31a, a resin package RP is molded to encloseeach pair of cup end 24 and wire bonding end 25 located closer to thefirst tie bar 22a, as shown in FIG. 4. A similar molding operation isalso performed in the second molding unit 31b with respect to each pairof cup end 24 and wire bonding end 25 located closer to the second tiebar 22b. The resin package RP may be made of a transparent thermosettingresin such as epoxy to have a generally bullet form although it may beotherwise shaped.

In each of the first and second molding units 31a, 31b, the packagemolding operation is normally performed batchwise for plural pairs oflead extensions 23a', 23c' or 23b', 23d' located closer to thecorresponding tie bar 22a or 22b. Thus, at the respective molding units,the continuous frame 21 need be transferred intermittently by apredetermined length which corresponds to the plural pairs of leadextensions.

On the other hand, the bonding operation is performed individually foreach pair of lead extensions 23a', 23c' or 23b', 23d'. Thus, at therespective bonding units 28a, 28b, the continuous frame 21 need betransferred constantly by a small amount corresponding to the pitchbetween the respective pairs of lead extensions.

According to the illustrated embodiment, a first buffer or excessportion 32 is formed in the frame 21 between the second bonding unit 28band the first molding unit 31a, as shown in FIG. 2. This buffer portion32 compensates for the above-described difference in transfer modebetween the bonding operation and the molding operation.

As clearly appreciated in FIG. 2, the frame 21 is twisted by 90° beforeentering the first molding unit 31a, and additionally twisted by 180°between the first and second molding units 31a, 31b. Such twisting makeseach pair of cup end 24 and wire bonding end 25 to be directedvertically downward at the time of molding, so that the pair of cup end24 and wire bonding end 25 is conveniently dipped, from above, in afluid resin loaded in a mold recess which is upwardly open. Further, the180° twisting between the first and second molding units 31a, 31benables these molding units to have an identical structure, therebycontributing to a cost reduction.

After passing the second molding unit 31b, the frame 21 is twisted by90° and merges in a second buffer or excess portion 33. Then, the frameenters the frame cutting unit 34 and moves therethrough substantiallycontinuously. At this time, the second buffer portion 33 compensates forthe difference between the intermittent transfer in the respectivemolding units 31a, 31b and the continuous transfer in the frame cuttingunit 34.

In the frame cutting unit 34, the first and third leads 23a, 23c in eachlead group are cut off the second tie bar 22b adjacent thereto, whereasthe second and fourth leads 23b, 23d in each lead group are cut off thefirst tie bar 22a adjacent thereto, as shown in FIG. 5. As a result, theframe 21 is separated into a first frame portion 21a associated with thefirst tie bar 22a, and a second frame portion 21b associated with thesecond tie bar 22b. Each of the frame portions 21a, 21b carries aplurality of unit LEDs connected to the corresponding tie bar 22a or 22badjacent to the respective resin packages RP at a constant pitch.

Then, each of the respective frame portions 21a, 21b with the connectedLEDs is passed through subsequent process units (not shown) such as aninspection unit. Apparently, the use of the frame portions 21a, 21benables continuous transfer, so that the subsequent process steps may beperformed very efficiently.

Finally, each of the LEDs is cut off the corresponding tie bar 22a or22b to provide a final product, as shown in FIG. 6.

According to the present invention, the respective extensions 23a', 23c'of the first and third leads 23a, 23c provide first side pairs of cupend 24 and wire bonding end 25 located closer to the first tie bar 22a,whereas the respective extensions 23b', 23d' of the second and fourthleads 23b, 23d provide second pairs of cup end 24 and wire bonding end25 located closer to the second tie bar 22b. In other words, both sidesof the frame 21 are utilized for providing pairs of cup end 25 and wirebonding end 25. Thus, the number of LEDs obtainable from a unit lengthof the frame 21 is almost doubled while ensuring a sufficient spacingbetween two adjacent LEDs as required for formation of the resin packageRP with a suitable size. As a result, it is possible to realize a greatmaterial saving and a reduction of the production cost.

On the other hand, the continuous nature of the frame 21 facilitateslongitudinal transfer through the different process units and thecontinuity of the process steps, as opposed to the use of theconventional strip-like frames which need be handled and transferredseparately. Thus, the manufacturing apparatus 27 as a whole can besimplified in configuration, and the production efficiency is greatlyimproved.

Further, the continuous nature enables the frame 21 to be easily twistedduring transfer. Such twistability of the frame 21 is advantageous atleast for the following reasons.

First, the two process units assigned to perform the same process stepon the different sides of the frame 21 can be made to have the samestructure, thereby additionally contributing to the cost reduction. Inthe illustrated embodiment for example, the first and second bondingunits 28a, 28b are made to have the same structure, as also are thefirst and second molding units 31a, 31b.

Secondly, the frame 21 can be made to assume a posture or orientationwhich is most suitable for any particular process step. In theillustrated embodiment for example, the frame 21 is vertically orientedin each of the respective molding units 31a, 31b, so that the moldingoperation can be conveniently performed.

The present invention is not limited to the specific embodimentdescribed herein and illustrated in the accompanying drawings. Forinstance, the first and second reinforcing bars 26a, 26b, thoughpreferable for improving supporting rigidity or stability for each pairof cup end 24 and wire bonding end 25, may be omitted.

According to the illustrated embodiment, the bonding operation isperformed separately with respect to both sides of the frame 21 in thefirst and second bonding units 28a, 28b, respectively. However, thebonding operation may be performed simultaneously with respect to bothsides of the frame 21 in a single bonding unit.

Further, the formation of the resin package RP (see FIG. 4) can beperformed in various ways which include the injection molding, and etc.

Finally, it should be understood that all such modifications as would beobvious to those skilled in the art art intended to be included in thescope of the present invention as defined in the appended claims.

I claim:
 1. An LED manufacturing frame comprising:a first tie barextending longitudinally of the frame; a second tie bar also extendinglongitudinally of the frame and transversely spaced from the first tiebar substantially in parallel thereto; first side pairs of chip bondingand wire bonding lead ends arranged transversely outwardly of the firsttie bar away from the second tie bar substantially at a constant pitch;and second side pairs of chip bonding and wire bonding lead endsarranged transversely outwardly of the second tie bar away from thefirst tie bar substantially at the same pitch as the first side pairs ofchip bonding and wire bonding lead ends.
 2. The frame according to claim1, wherein the first and second tie bars are connected together byplural groups of first to fourth consecutive leads, the first side pairsof chip bonding and wire bonding lead ends being provided by respectiveextensions of the first and third leads, the second side pairs of chipbonding and wire bonding lead ends being provided by respectiveextensions of the second and fourth leads.
 3. The frame according toclaim 1, wherein each of the chip bonding lead ends has a cup form. 4.The frame according to claim 2, wherein the respective extensions of thefirst and third leads are connected together by a first reinforcing barextending laterally outwardly of the first tie bar in parallel thereto,the respective extensions of the second and fourth leads being alsoconnected together by a second reinforcing bar extending laterallyoutwardly of the second tie bar in parallel thereto.
 5. The frameaccording to claim 1, wherein the frame is substantially continuous.